One Trip Metal Seal Tieback Connection to Wellhead with Telescoping Joint

ABSTRACT

A tieback string assembly features a metal to metal nose seal weighted down with casing extending between a lower end of a telescoping joint optionally having metal to metal seals for spacing out to a wellhead casing hanger. The telescoping joint is located so that the hanging weight off the telescoping joint lower end is sufficient to energize the metal to metal nose seal engaged to a sleeve or a liner top packer. The tieback string is smaller in outside diameter than the parent casing through which it is run. The assembly retains high pressure by avoiding lower pressure rated elastomers in the nose seal or the telescoping joint.

FIELD OF THE INVENTION

The field of the invention is tieback connections to a wellhead requiring specific space out in applications where metal to metal seals for high pressure applications are needed.

BACKGROUND OF THE INVENTION

In assembling subsea wells there is often a distance that needs to be spanned between an upper end of a tubing string or an isolation packer and the wellhead. Frequently, in deep wells this distance could be 1524 meters or more. The spacing between the lower support location and a hanger in the wellhead needs to be closely approximated by the length of the assembled string in between. Stretch of the tubulars under their own weight complicates this space out. In the past this required what was called a dummy run where the string was landed on the lower support and assembled to the wellhead hanger location. The offset from the desired dimension was marked by closing BOP rams on painted DP joints. The string was then pulled so that sections could be replaced with different lengths and another trip in the hole was made to get the optimum spacing between the tubing or packer support in the wellbore and the wellhead hanger. On offshore applications this could be very costly in view of the additional rig time needed to make the additional trip and rig up and rig down casing equipment again.

Metal to metal tieback seals were developed by Baker Hughes, a GE company but they required continuous weight to hold a sealing connection. Due to thermal expansion or contraction concerns it was not certain in the past that such a connection would have the requisite weight on the connection, which forced the joint to be cemented to hold the connection together. The need to cement also added logistical complexities and cost particularly in offshore applications.

Telescoping joints have been developed to address the space out issue by allowing as much as 7 meters leeway to connect to the wellhead hanger and avoid making a dummy run. Telescoping joints for subsea use are described in U.S. Pat. No. 9,664,000; 2015/0129240; U.S. Pat. No. 5,090,737 and U.S. Pat. No. 3,667,547.

What has not been available and is addressed by the present invention is a way to provide metal to metal tieback seal and keep it operative without a need to cement as in the past in a tieback string that saves a dummy run but at the same time allows for high pressure connections using metal to metal sealing optionally including the seals in a telescoping space out joint. The joint is located in the string at a depth where the weight of string connected to the lower end of the telescoping joint provides the weight to keep a metal to metal seal weighted so that it will function without a need for a cementing job, although cementing can still be optionally done. These and other aspects of the present invention can be more readily understood from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention can be determined from the appended claims.

SUMMARY OF THE INVENTION

A tieback string assembly features a metal to metal nose seal weighted down with casing extending between a lower end of a telescoping joint also optionally having metal to metal seals for spacing out to a wellhead casing hanger. The telescoping joint is located so that the hanging weight off the telescoping joint lower end is sufficient to energize the metal to metal nose seal engaged to a sleeve or a liner top packer. The tieback string is smaller in outside diameter than the parent casing through which it is run. The assembly retains high pressure by avoiding lower pressure rated elastomers in the nose seal or the telescoping joint.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a part section view of a tieback string with metal to metal connections with a telescoping joint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a profiled sleeve or existing liner top packer 10 into which a nose seal 14 that is metal to metal at the lower end of a tieback string 12 is set. To keep the needed weight on the seal 14 the length of the string between a lower end 16 of a telescoping joint 18 that has metal to metal seal 20 provided. The telescoping joint is positioned so that the weight of the string from the lower end 16 down to the nose seal 14 is at least the weight necessary to keep the connection integrity to contain high pressure as the telescoping joint 18 gets longer and shorter during normal operation. The use of the telescoping joint 18 also allows as much as 7 meters tolerance for initial space out to connect to the wellhead hanger 22 without making a dummy run to adjust for perfect space out.

For operators with needs to contain high pressure in deep wells the combination of a telescoping joint placed in a string at a precise location so that hanging weight off the joint 18 satisfies the need to keep a predetermined weight on the metal to metal seal 14 when used in combination with a joint 18 that features metal seals as well, the assembly described provides the solution.

The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: 

1. A method of connecting a tieback string to a wellhead hanger, comprising: providing a metal to metal nose seal on a lower end of a tieback string; connecting said nose seal to an existing string in the borehole; locating a telescoping joint in the tieback string in a position where a lower portion of the tieback string connected to a lower portion of the telescoping joint provides weight needed to keep said nose seal activated.
 2. The method of claim 1, comprising: providing a metal to metal seal in said telescoping joint.
 3. The method of claim 1, comprising: cementing around said nose seal when said nose seal is connected to the existing string.
 4. The method of claim 1, comprising: using the telescoping joint to adjust the length of the tieback string for connection to the wellhead. 